Cabbage Worms: Identification, Control & Prevention

Cabbage worms (imported cabbageworms, larvae of Pieris rapae white butterflies) target cabbage, kale, cauliflower, broccoli. Minor leaf holes are tolerable; real damage occurs during seedling establishment and early head formation.

Identification

Velvety green larvae with faint yellow stripes. Not to be confused with cabbage loopers (yellow-green, humping movement). Adults: white butterflies with black markings, laying eggs on leaf undersides. Also watch for diamondback moth and zebra caterpillar—camouflage experts; their frass (droppings) often gives them away.

Damage

Feed on foliage and heads, leaving only stems and large veins. Can devour crops; frass stains produce.

Control

• Handpick eggs/larvae.
• Yellow sticky traps catch butterflies (may catch beneficials).
• Btk (Bacillus thuringiensis var. kurstaki) every 1–2 weeks; Sevin also effective. Wash harvest with water + detergent.
• Damp leaves + cornmeal: caterpillars eat, swell, die.
• Check local extension for chemicals.
• Old remedy: rye flour dust dehydrates worms.

Prevention

• Row covers deter egg-laying.
• Trichogramma wasps parasitize eggs (mail-order; timing critical).
• Companion planting: thyme repels; mustard traps (destroy infested).
• Red-leaved cabbage varieties—worms can't camouflage.

Plants Affected

• Cabbage
• Kale
• Cauliflower
• Broccoli